Infrared emission and the destruction of dust in HII regions

Pavlyuchenkov, Ya. N.; Kirsanova, M. S.; Wiebe, D. S.

doi:10.1134/s1063772913070056

Cited by 59 publications

(91 citation statements)

References 23 publications

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“…It has been demonstrated that a non-negligible fraction of the 70 μm emission comes from stochastically heated very small grains (e.g., Compiègne et al 2010;Pavlyuchenkov et al 2013); this is especially true when an H ii region is present along the line of sight.…”

Section: Physical Conditions Of the Cold Ismmentioning

confidence: 99%

“…The 24 μm emission is bright in the direction of the center of the H ii region, a region devoid of PAHs emission. As shown by the radiative transfer model of Pavlyuchenkov et al (2013) this emission comes from very small dust grains (VSGs; a few nm in size) located inside the ionized region, and out of thermal equilibrium after absorption of ionizing photons. Diffuse 24 μm emission is also observed in the direction of the neutral PDR surrounding the ionized region.…”

Section: Distance Morphology and Nature Of The Ionized Gasmentioning

confidence: 99%

“…The 8.0 μm emission displays a central cavity surrounded by a roughly thin annular shell emission. The 8.0 μm IRAC band contains emission bands at 7.7 μm and 8.6 μm, commonly attributed to polycyclic aromatic hydrocarbon (PAH) molecules; PAHs are believed to be destroyed in the ionized gas (Pavlyuchenkov et al 2013), but are thought to be excited in the photo-dissociation region (PDR) at the interface of the H ii region and molecular cloud by the absorption of far-UV photons from the exciting stars of the H ii regions. The 8.0 μm IRAC diffuse emission is extended, well beyond the main shell, possibly because of the leakage of UV photons through holes into the neutral material.…”

Section: Distance Morphology and Nature Of The Ionized Gasmentioning

confidence: 99%

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The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

Samal

Zavagno

Deharveng

et al. 2014

A&A

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Aims. We investigate the star formation activity in the molecular complex associated with the Galactic H ii region Sh2-90.Methods. We obtain the distribution of the ionized and cold neutral gas using radio-continuum and Herschel observations. We use near-infrared and Spitzer data to investigate the stellar content of the complex. We discuss the evolutionary status of embedded massive young stellar objects (MYSOs) using their spectral energy distribution.Results. The Sh2-90 region presents a bubble morphology in the mid-infrared. Radio observations suggest it is an evolved H ii region with an electron density ∼144 cm −3 , emission measure ∼6.7 × 10 4 cm −6 pc and an ionized mass ∼55 M . From Herschel and CO (J = 3−2) observations we found that the H ii region is part of an elongated extended molecular cloud (H 2 column density ≥3 × 10 21 cm −2 and dust temperature 18−27 K) of total mass ≥1 × 10 4 M . We identify the ionizing cluster of Sh2-90, the main exciting star being an O8-O9 V star. Five cold dust clumps, four mid-IR blobs around B stars, and a compact H ii region are found at the edge of the bubble. The velocity information derived from CO data cubes suggest that most of them are associated with the Sh2-90 region. One hundred and twenty-nine low mass (≤3 M ) YSOs have been identified, and they are found to be distributed mostly in the regions of high column density. Four candidate Class 0/I MYSOs have been found. We suggest that multi-generation star formation is present in the complex. From evidence of interaction, time scales involved, and evolutionary status of stellar/protostellar sources, we argue that the star formation at the edges of Sh2-90 might have been triggered. However, several young sources in this complex are probably formed by some other processes.

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Section: Physical Conditions Of the Cold Ismmentioning

confidence: 99%

Section: Distance Morphology and Nature Of The Ionized Gasmentioning

confidence: 99%

Section: Distance Morphology and Nature Of The Ionized Gasmentioning

confidence: 99%

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The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

Samal

Zavagno

Deharveng

et al. 2014

A&A

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“…Following Pavlyuchenkov et al (2013), we consider that the dust filling the H II region and penetrating into the bow shock is similar of that of the ISM. Our radiative transfer calculations nevertheless suffer from uncertainties regarding to the composition of this ISM dust.…”

Section: Surrounding H II Region and Dust Compositionmentioning

confidence: 99%

Bow shock nebulae of hot massive stars in a magnetized medium

Meyer

Mignone

Kuiper

et al. 2016

Mon. Not. R. Astron. Soc.

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A significant fraction of OB-type, main-sequence massive stars are classified as runaway and move supersonically through the interstellar medium (ISM). Their strong stellar winds interact with their surroundings where the typical strength of the local ISM magnetic field is about 3.5-7 µG, which can result in the formation of bow shock nebulae. We investigate the effects of such magnetic fields, aligned with the motion of the flow, on the formation and emission properties of these circumstellar structures. Our axisymmetric, magneto-hydrodynamical simulations with optically-thin radiative cooling, heating and anisotropic thermal conduction show that the presence of the background ISM magnetic field affects the projected optical emission our bow shocks at Hα and [OIII] λ 5007 which become fainter by about 1-2 orders of magnitude, respectively. Radiative transfer calculations against dust opacity indicate that the magnetic field slightly diminishes their projected infrared emission and that our bow shocks emit brightly at 60 µm. This may explain why the bow shocks generated by ionizing runaway massive stars are often difficult to identify. Finally, we discuss our results in the context of the bow shock of ζ Ophiuchi and we support the interpretation of its imperfect morphology as an evidence of the presence of an ISM magnetic field not aligned with the motion of its driving star.

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“…IR observations of thermal dust emission is an attractive possibility because winds from hot stars are dust-free, whereas H  regions contain a normal ISM dust distribution, with the exception of PAHs that are destroyed by ionizing radiation (Povich et al 2007;Pavlyuchenkov et al 2013). O stars are luminous radiation sources, and so even though only a small fraction of the stellar radiation is absorbed by dust, the re-emitted radiation is often more luminous than that of all gas-cooling radiation (Meyer et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Detecting stellar-wind bubbles through infrared arcs in H ii regions

Mackey

Haworth

Gvaramadze

et al. 2016

A&A

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Mid-infrared arcs of dust emission are often seen near ionizing stars within H  regions. A possible explanations for these arcs is that they could show the outer edges of asymmetric stellar wind bubbles. We use two-dimensional, radiation-hydrodynamics simulations of wind bubbles within H  regions around individual stars to predict the infrared emission properties of the dust within the H  region.We assume that dust and gas are dynamically well-coupled and that dust properties (composition, size distribution) are the same in the H  region as outside it, and that the wind bubble contains no dust. We post-process the simulations to make synthetic intensity maps at infrared wavebands using the  code. We find that the outer edge of a wind bubble emits brightly at 24 µm through starlight absorbed by dust grains and re-radiated thermally in the infrared. This produces a bright arc of emission for slowly moving stars that have asymmetric wind bubbles, even for cases where there is no bow shock or any corresponding feature in tracers of gas emission. The 24 µm intensity decreases exponentially from the arc with increasing distance from the star because the dust temperature decreases with distance. The size distribution and composition of the dust grains has quantitative but not qualitative effects on our results. Despite the simplifications of our model, we find good qualitative agreement with observations of the H  region RCW 120, and can provide physical explanations for any quantitative differences. Our model produces an infrared arc with the same shape and size as the arc around CD −38• 11636 in RCW 120, and with comparable brightness. This suggests that infrared arcs around O stars in H  regions may be revealing the extent of stellar wind bubbles, although we have not excluded other explanations.

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Infrared emission and the destruction of dust in HII regions

Abstract: The generation of infrared (IR) radiation and the observed IR intensity distribution at wavelengths of 8, 24, and 100 µm in the ionized hydrogen region around a young, massive star is investigated. The evolution of the HII region is treated

Cited by 59 publications

References 23 publications

The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

The molecular complex associated with the Galactic H II region Sh2-90: a possible site of triggered star formation

Bow shock nebulae of hot massive stars in a magnetized medium

Detecting stellar-wind bubbles through infrared arcs in H ii regions

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